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Post subject: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 2:09 pm
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I'm working on a 1966 Princeton that has been totally "Weber'd" per the "Save that Princeton" chapter in his book. I bought it this way and would never have done this but it is an interesting project for me to learn on.

It has resistors on the power tubes that have drifted and I'm ordering parts. They are 470 Ohm resistors from pin 4 to 6 on both tubes. Should I use 1W Metal Oxide or 1/2 somethings?

The blue resistor and black resistor:
Image

A quick gut shot, lots of mods, tremolo removed, 2112 transformer added:
Image

It came like this, the tolex was stapled in place, broken baffle etc etc It was a mess:
Image

If you care to look at more pictures:
http://s1046.photobucket.com/user/jjhun ... ject%20Amp


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Post subject: Re: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 2:53 pm
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Those 470K resistors don't even belong in a Princeton Reverb.

Has that amp been modded for 6L6's?

Arjay

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Post subject: Re: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 3:07 pm
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Huntslab, Arjay is correct. The PR draws its screen voltage, after a 1K-ohm, 1-watt dropping resistor in the PS rail.

http://www.webphix.com/schematic%20heav ... aa1164.pdf


Whereas, most 6L6GC and the DR draw their screen voltage after a low DCR choke (maybe a few ohms), Thus, the need to run separated 470-ohm resistor onto the screen to insure that this grid is running a good 5VDC below the anode plates.

http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 3:16 pm
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The "creative" filter cap array is also noteworthy.

:shock:

Arjay

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Post subject: Re: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 3:25 pm
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Thanks for the reply's. In Gerald Webers book, Tube Amp Talk etc there is a chapter called "Save That Princeton" (Not the same title I would have used)

This is what was done before I got it:
Remove the vibrato circuit
Rewire the phase inverter
Move phase inverter supply voltage
Install Presence control, they used the speed pot
Change Feedback resistor
Change transformer to Kendrick 2112 AHR
Add a 12" speaker

Here is a schematic of what was done:
Image


It seemed to work when I got it and then since it had so many problems I put it away back in 2005. I repaired the cab and had it professionally recovered, looks good now.

When I fired up the amp I checked bias: 436 Plate V / about 17 on the weber bias rite. Sounded great for ten minutes, poped a few times, then volume dropped and signal was distorted.

I believe you can run 6L6CG's in it with this 2112 AHR transformer:
http://www.kendrick-amplifiers.com/mm5/ ... _Code=0602

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Post subject: Re: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 3:26 pm
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Retroverbial wrote:
The "creative" filter cap array is also noteworthy.

:shock:

Arjay


Yeah, sweet job, not.... I have a new cap can on the way and they will be gone.

Image

Image

Image


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Post subject: Re: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 3:30 pm
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And the light green wire is 300v, should that be replaced with some 600v wire?


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Post subject: Re: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 3:33 pm
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The adjustable bias pot is the sanest mod I've seen on this chassis.

Arjay

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Post subject: Re: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 4:08 pm
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Retroverbial wrote:
The adjustable bias pot is the sanest mod I've seen on this chassis.

Arjay


Yeah it is a mess. I'm trying to get it going the way it is for starters. I want to hear what the mods sound like. If it isn't great, I will gut it and try to take it back to a stock Princeton.


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Post subject: Re: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 4:28 pm
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I would waist my time just get it back to stock with a 12 in speaker and be very happy


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Post subject: Re: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 5:34 pm
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The 12-inch speaker can be a worthwhile mod depending upon how professional the conversion job is. For a vintage piece such as this though, I'd build an all-new baffle-board rather than hack up a vintage piece of lumber.

Arjay

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Post subject: Re: Resistor Question 66 Princton
Posted: Fri Jun 14, 2013 10:19 pm
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Retroverbial wrote:
The 12-inch speaker can be a worthwhile mod depending upon how professional the conversion job is. For a vintage piece such as this though, I'd build an all-new baffle-board rather than hack up a vintage piece of lumber.

Arjay


Here is the cab now. I kept it 12" and built a new baffle and had a pro recover and grill it. Baffle was busted badly when I got it. Had to be done....

Image

Image


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Post subject: Re: Resistor Question 66 Princton
Posted: Sat Jun 15, 2013 2:03 am
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A vintage Jensen C12Q or P12Q would yield a warmer, more compressed tone when the amp is driven hard and deliver something closer to the authentic Fender sound. For additional punch, a JBL D120F might be the ticket.

Arjay

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Post subject: Re: Resistor Question 66 Princton
Posted: Sat Jun 15, 2013 9:41 am
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That was the speaker it came with and it is not good. I have a Vintage 30 that may go in there or an orange D120f. Gotta get the guts working before it is speaker time...

Is that 300v wire ok, the light green wire or do I need 600v?


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Post subject: Re: Resistor Question 66 Princton
Posted: Sat Jun 15, 2013 10:16 am
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I'd feel more comfortable with the heavier-gauge wire, preferably with cloth push-back insulation to match the original spec.

Arjay

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